The present invention relates to reaction of heterocyclic monomers or oligomers with certain dopants in the presence of certain solvents to form solutions, and to solutions of polyheteroaromatics and articles cast therefrom.
Conductive solutions of polymers such as poly(phenylene sulfide) are described U.S. Pat. No. 4,452,727 to Frommer et al. (June 5, 1984) formed by reacting the polymer, a solvent such as liquid arsenic trifluoride and an acceptor dopant such as arsenic pentafluoride. It had previously been indicated in U.S. Pat. No. 4,375,427 to Ivory et al. (Mar. 1. 1983) that gaseous arsenic trifluoride improves the doping of solid poly(phenylene sulfide) by arsenic pentafluoride. In both of these patents and related articles, benzothiophene structures are indicated as forming in poly(phenylene sulfide) when acceptor doped.
Heterocyclic polymers such as polythiophene, polypyrrole, poly-N-methylpyrrole, poly-3-methylthiophene and poly-3,4-dimethylthiophene have been prepared and acceptor-doped to conductivities in the same general range (10.sup.-6 to 1 S/cm) common for acceptor-doped poly(phenylene sulfide). Normally, however, these heterocyclic polymers are prepared from the monomers electrochemically, thereby simultaneously polymerizing and doping. Such electrochemical preparation commonly results, however, in poor yields and enables only the formation of insoluble thin films on conductive substrates or peeled off of such substrates. The ability to process doped polymers is limited. Some of these heterocyclic polymers have also been prepared chemically (see EPO, 95,412 of Thompson-CSF and EPO 97,893 of Bayer AG) and then doped chemically. See also G. Kossmehl et al., Makromol, Chem., Rapid, Commun., Vol. 2, pp. 551-555 (1981). Here, uniform doping of desirable shapes can be awkward, complex or impossible.
Certain conductive polymers are known to polymerize further in the solid state (e.g. from oligomers to higher polymers) when doped. U.S. Pat. No. 4,440,069 to Ivory et al. (Apr. 3, 1984) discloses such polymerization at col. 5, lines 57-68 and Examples 8-11 for phenylene oligomers.